ALMA High-frequency Long Baseline Campaign in 2021: Highest Angular Resolution Submillimeter Wave Images for the Carbon-rich Star R Lep

arXiv (Cornell University)

Abstract

The Atacama Large Millimeter/submillimeter Array (ALMA) was used in 2021 to image the carbon-rich evolved star R Lep in Bands 8-10 (397-908 GHz) with baselines up to 16 km. The goal was to validate the calibration, using band-to-band (B2B) phase referencing with a close phase calibrator J0504-1512, 1.2 deg from R Lep in this case, and the imaging procedures required to obtain the maximum angular resolution achievable with ALMA. Images of the continuum emission and the hydrogen cyanide (HCN) maser line at 890.8 GHz, from the J=10-9 transition between the (1110) and (0400) vibrationally excited states, achieved angular resolutions of 13, 6, and 5 mas in Bands 8-10, respectively. Self-calibration (self-cal) was used to produce ideal images as to compare with the B2B phase referencing technique. The continuum emission was resolved in Bands 9 and 10, leaving too little flux for self-cal of the longest baselines, so these comparisons are made at coarser resolution. Comparisons showed that B2B phase referencing provided phase corrections sufficient to recover 92%, 83%, and 77% of the ideal image continuum flux densities. The HCN maser was sufficiently compact to obtain self-cal solutions in Band 10 for all baselines (up to 16 km). In Band 10, B2B phase referencing as compared to the ideal images recovered 61% and 70% of the flux density for the HCN maser and continuum, respectively.

Authors 13

1. Yoshiharu Asaki
2. Luke T. Maud Aachen Allegro

   Leiden University · European Southern Observatory · Leiden Observatory

   Affiliation as printed

   Allegro , Leiden Observatory , Leiden University , PO Box 9513 , 2300 RA Leiden , The Netherlands

   ESO Headquarters , Karl-Schwarzchild-Str 2 D-85748 Garching , Germany

3. Harold Francke

   Atacama Large Millimeter Submillimeter Array

   Affiliation as printed

   Joint ALMA Observatory Alonso de Córdova 3107 , Vitacura 763 0355 , Santiago , Chile

4. Hiroshi Nagai
5. D. Petry
6. Edward B. Fomalont
7. E. M. L. Humphreys
8. Anita M. S. Richards
9. K. T. Wong
10. William R. F. Dent

    Atacama Large Millimeter Submillimeter Array

    Affiliation as printed

    Joint ALMA Observatory Alonso de Córdova 3107 , Vitacura 763 0355 , Santiago , Chile

11. Akihiko Hirota

    Atacama Large Millimeter Submillimeter Array · National Astronomical Observatory of Japan

    Affiliation as printed

    Joint ALMA Observatory Alonso de Córdova 3107 , Vitacura 763 0355 , Santiago , Chile

    National Astronomical Observatory of Japan , Los Abedules 3085 Oficina 701 , Vitacura 763 0414 , Santiago , Chile

12. Satoko Takahashi

    National Astronomical Observatory of Japan

    Affiliation as printed

    National Astronomical Observatory of Japan , 2-21-1 Osawa , Mitaka , Tokyo 181-8588 , Japan

13. Antonio S. Hales

    National Radio Astronomy Observatory · Atacama Large Millimeter Submillimeter Array

    Affiliation as printed

    Joint ALMA Observatory Alonso de Córdova 3107 , Vitacura 763 0355 , Santiago , Chile

    National Radio Astronomy Observatory , 520 Edgemont Rd. Charlottesville , VA 22903 , USA